SkyTrekker

1970 M20E Top Cowl Cracks around Oil Access Door

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I've done my best searching for posts here related to the top cowl cracking around the oil access door, but all I'm finding are posts on the later model fiberglass tops.

When I bought the E in May of last year, I noted, and it was reflected on the pre-buy, that there were thin cracks (one about an inch and a half long) in the top cowl starting at the outer corners of the hinge points, moving away from the oil door.  The cracks had been stop-drilled at a couple of points and the (well-known and respected on this forum) IA did not make a special point of it to me, so I assumed it was a common thing.

Today I noticed that while the cracks have not pushed past the drill points, a small triangular piece (~1/8") of the top cowl abutting one of the cracks at one off the edges has come off, and a hinge (or repair) rivet that was previously there is gone.  During flight, I've noticed that the oil door corners vibrate up away from the cowl top in a very high frequency flutter.  It did that from the beginning, but now it seems to be fluttering up a little higher above the cowl than before.

A few questions:

  • Is this something that happens often?  I can't find a single reference anywhere.
  • Is there any way to 'more permanently' fix the cowl cracks?
  • Or is my only real option to replace the entire top cowl? (Which sounds daunting, and expensive, since I understand each of our planes is hand built and no two are identical.)
  • It is making me uneasy since I have to think that the vibrations will cause the cracks to grow and ultimately the oil access door and (possibly more) will separate during flight and crack the windshield or damage the rudder or elevator controls. Does that sound about right?

Appreciate any insight or thoughts, especially from those who have observed this condition before.  

 

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Starting with the usual points...

The 1970E cowl is all aluminum...

It has some pretty highly stressed areas from the original molding process...

It may have gotten pretty dinged up during every annual since the first one...

The amount of vibration the engine generates is pretty high while operating normally...

This pretty much explains the crack that was on the nose of my 65C’s cowl...

 

There are a few ways to minimize vibrations...

  • avoid yellow arcs on the tach...
  • dynamic balance the prop...
  • get GAMI injectors for the FI system...
  • got a JPI? How is the Gami spread...?
  • get modern engine rubber mounts...

Finishing with how daunting this is.... It isn’t really.  Our planes are hand built from identical parts made with some pretty exacting tolerances... finding some used cowl parts is quite plausible.... but they will come with 50 years of wear and tear on them....

While you are looking....  Check out the recent upgrades for your cowling mentioned around here.  If you are going to spend some money... might as well get some improvements to speeed and cooling...

Got any pics?

Best regards,

-a-

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Thanks for the thoughts, @carusoam

I was planning on having the prop dynamically balanced, but am moving that up to asap due to the impact of vibrations to this issue.  I always avoid my red arc on my tach (I don't have any yellow on mine :-)  Been considering installing GAMI injectors at some point.  Rubber engine mounts sound like a good idea.

That said, and either way, I'll need to repair this.  Trying to understand what my options are, and what the implications of the current condition of the cowl are.

Here is a pic.  This frame looks like it captured the fluttering when the door was at its highest point of cycle, furthest way from the rest of the cowl surface.  I circled the drill points and the arrow points to the missing rivet and missing small section of cowl surface that I mentioned in opening post.

575033156_OilAccessDoor.thumb.jpg.06b1758a8db3451a0c6e166717a973a8.jpg

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That doesn’t look very original...

Could be a different hinge...

looks like the bend doesn’t match the cowl...

The latches may be newer than 1970...

Park next to another E if you can, to see what the finer details may be...

it kind of looks like the door may have been replaced from something else...

Whatever it is, may be causing the strain.  150mph causes some pretty large forces on things that stand out...

Got any notes in the logs about it?

My 65C had two doors on the cowl.  One for the oil access, the other a battery access point.  Both were 1/4 turn type of fasteners...

PP thoughts only, not a mechanic...

Best regards,

-a-

 

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2 hours ago, SkyTrekker said:

Thanks for the thoughts, @carusoam

I was planning on having the prop dynamically balanced, but am moving that up to asap due to the impact of vibrations to this issue.  I always avoid my red arc on my tach (I don't have any yellow on mine :-)  Been considering installing GAMI injectors at some point.  Rubber engine mounts sound like a good idea.

That said, and either way, I'll need to repair this.  Trying to understand what my options are, and what the implications of the current condition of the cowl are.

Here is a pic.  This frame looks like it captured the fluttering when the door was at its highest point of cycle, furthest way from the rest of the cowl surface.  I circled the drill points and the arrow points to the missing rivet and missing small section of cowl surface that I mentioned in opening post.

575033156_OilAccessDoor.thumb.jpg.06b1758a8db3451a0c6e166717a973a8.jpg

Replacement of the entire top would be overkill.  Some form of reinforcing doubler on the inner surface of the cowl should stop further growth.

Clarence

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I've done my best searching for posts here related to the top cowl cracking around the oil access door, but all I'm finding are posts on the later model fiberglass tops.
When I bought the E in May of last year, I noted, and it was reflected on the pre-buy, that there were thin cracks (one about an inch and a half long) in the top cowl starting at the outer corners of the hinge points, moving away from the oil door.  The cracks had been stop-drilled at a couple of points and the (well-known and respected on this forum) IA did not make a special point of it to me, so I assumed it was a common thing.
Today I noticed that while the cracks have not pushed past the drill points, a small triangular piece (~1/8") of the top cowl abutting one of the cracks at one off the edges has come off, and a hinge (or repair) rivet that was previously there is gone.  During flight, I've noticed that the oil door corners vibrate up away from the cowl top in a very high frequency flutter.  It did that from the beginning, but now it seems to be fluttering up a little higher above the cowl than before.
A few questions:
  • Is this something that happens often?  I can't find a single reference anywhere.
  • Is there any way to 'more permanently' fix the cowl cracks?
  • Or is my only real option to replace the entire top cowl? (Which sounds daunting, and expensive, since I understand each of our planes is hand built and no two are identical.)
  • It is making me uneasy since I have to think that the vibrations will cause the cracks to grow and ultimately the oil access door and (possibly more) will separate during flight and crack the windshield or damage the rudder or elevator controls. Does that sound about right?
Appreciate any insight or thoughts, especially from those who have observed this condition before.  
 


I think a doubler repair that wraps around that corner where the crack originated will be adequate. Certainly would not replace the entire cowl for that.


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There is already a second piece of alum under that piece to form the ledge for the oil door.   Just pull that piece out make a bigger one with some flush rivets and touch it up with some paint.  Needs to be tied into the hinge rivets.   The more you ignore it, the worse it will be to repair.

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4 hours ago, carusoam said:

That doesn’t look very original...

Could be a different hinge...

looks like the bend doesn’t match the cowl...

The latches may be newer than 1970...

Park next to another E if you can, to see what the finer details may be...

it kind of looks like the door may have been replaced from something else...

Whatever it is, may be causing the strain.  150mph causes some pretty large forces on things that stand out...

Got any notes in the logs about it?

My 65C had two doors on the cowl.  One for the oil access, the other a battery access point.  Both were 1/4 turn type of fasteners...

PP thoughts only, not a mechanic...

Best regards,

-a-

 

Nah, that looks just like the two doors on my also-1970 cowl, with flip-up latches.

I would also recommend adding a doubler plate beneath it and riveting it down again.

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I agree with a doubler, just make sure it goes past the crank. How sloppy is the hinge? Might be a good time to replace it as well

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16 hours ago, SkyTrekker said:

Thanks for the thoughts, @carusoam

I was planning on having the prop dynamically balanced, but am moving that up to asap due to the impact of vibrations to this issue.  I always avoid my red arc on my tach (I don't have any yellow on mine :-)  Been considering installing GAMI injectors at some point.  Rubber engine mounts sound like a good idea.

That said, and either way, I'll need to repair this.  Trying to understand what my options are, and what the implications of the current condition of the cowl are.

Here is a pic.  This frame looks like it captured the fluttering when the door was at its highest point of cycle, furthest way from the rest of the cowl surface.  I circled the drill points and the arrow points to the missing rivet and missing small section of cowl surface that I mentioned in opening post.

575033156_OilAccessDoor.thumb.jpg.06b1758a8db3451a0c6e166717a973a8.jpg

I have the exact same access door. Looking at your picture, it looks like the door is sitting high and it also looks like the door may have popped open in flight at some point. I'll post a picture of mine when I get a chance.

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Thanks everyone for the input! 

I'll check in with a shop to see about adding a doubler under the cracked areas.  The hinge is not sloppy, so I think we are good there.  

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